1. The cause of the odor is generally coming. There are two reasons for the odor of the composite product: one is the odor produced by the residual solvent; the second is the odor produced by the polyethylene resin. The two odors are different.
(1) Odor produced by residual solvents a. The solvents used in printing inks for composite products are generally high-boiling, odorous and toxic solvents such as ketones, xylene, toluene, and butanol; the pigment particles in the ink are very fine. Adsorption capacity is very strong, although it has been heated and dried at the time of printing, but due to the time and thoroughness; especially the larger amount of ink on the printed matter; its residual solvent more. If these residual solvents are brought into the compounding process, it will be more difficult to run off after compounding, so it will penetrate slowly.
In the above solvent; pay particular attention to the use of small amounts of butanone; it is best not to use it. Because the general ink is added with butanone at the time of preparation, if it is added at the time of opening, it is very easy to add too much solvent due to excessive addition of butanone, resulting in more obvious odor.
b. Residual solvent generated by the adhesive used in the compounding process.
c. Residual student solvents caused by AC.
(2) Odor produced by the resin.
Generally, in the T-die co-extruded polyethylene, odor oxidizes and enters the resin in a molten state at about 300°C.
2. Residual Dose Measurement Method The amount of residual solvent can be determined by gas chromatography or by gravimetric method. A weight determination method is described below.
The dried and uncomposited sample was taken out of the tunnel outlet and its size was 100mm x 100mm. Immediately put it on the analytical balance and call it mass W, then put it in a constant temperature oven at 105°C for 1 hour, take it out and cool it to room temperature in a desiccator, and then weigh the mass to W2 (when W2 is definitely higher than W1 To be smaller, this is because the residual solvent is volatilized), and then calculate the following formula:
R=(W1-2)/(0.10×0.10)
R-remaining solvent amount (g/m2)
The amount of residual solvent after compound drying in the country is controlled below 10mg/m2; in the United States and Japan, it is required to be controlled below 5mg/m2.
3. Ways to eliminate (reduce) odors (1) To ensure the product's drying quality (including drying in printing and drying in compounding). Whether it can be completely dry, mainly related to the drying capacity of the machinery and equipment, the speed of the ink, the amount of ink used, the solvent used in the ink, etc., the slower the vehicle speed, the lesser the amount of ink, and the faster solvent evaporation, the more drying of the printed matter. Thoroughly, on the contrary, it is more difficult to dry thoroughly.
In compounding, it is mainly related to the drying capacity, speed, glue concentration, and amount of glue on mechanical equipment. The slower the vehicle speed, the thinner the glue, and the smaller the amount of glue, the easier it is to dry completely. Otherwise, it is more difficult to dry completely. Completely dry, it can only eliminate some of the odors.
(2) To completely eliminate odors, do not use high-boiling inks, solvents, and adhesives that contain toxic, odor, and odor. Only low-boiling ethanol acetate, alcohol, ketones, isopropyl alcohol, etc. can be used. Poison, odorless solvent. Two-component high-performance, versatile polyurethane inks eliminate the need for aromatic hydrocarbon solvents, and alcohol-soluble inks do not have the above-mentioned disadvantages. If there is no problem with ink and glue and the amount of residual solvent is very small, there is basically no odor.
(3) For the odor generated by the resin, if possible, the melting temperature of the polyethylene should be reduced as much as possible, or the distance between the T-die and the press roller should be shortened, so that the odor can be minimized. .
Finally, the company is reminded to note that sometimes the composite product packaging bag does not smell or odor at room temperature, but when it is used to package foods that also contain heat (such as freshly baked biscuits from processing lines), it is cooled. When the food was tasted, there was a strong odor and odor. This was due to the excessive residual solvent, which caused the permeation and volatilization of the residual solvent when the temperature increased.